The former Hearts captain has failed to accept a contract offered to him by chief executive Craig Mather following a trial at Murray Park more than two weeks ago.
McCoist told RangersTV: "Sadly, that deal has gone dead at the moment and I think Marius has one or two other options.
"Craig effectively put an offer to him which wasn't met so we're just about closing that one off at this moment in time."
Rangers had also been in protracted talks with Bosnia-Herzegovina international Boris Pandza but they have confirmed those discussions ended. Pandza last week accused the club of being unprofessional for failing to come up with a concrete offer.
McCoist, who has been lining up with a central defence of Lee McCulloch and Bilel Mohsni, added: "It looks like we'll have to go with what we've got and, to be fair, we've been reasonably solid defensively.
"Hopefully we'll just carry a little bit of luck with injuries and suspensions and we'll see where that takes us.
"We've got options in guys like Sebastien (Faure) and Emilson (Cribari). Big Jig (McCulloch) has been playing at the back with Bilel but there are others too."
Two other centre-backs, Chris Hegarty and Ross Perry, are working back to fitness following ankle surgery.